Excavating equipment typically includes various wear parts to protect underlying products from premature wear. The wear part may simply function as a protector (e.g., a wear cap) or may have additional functions (e.g., an excavating tooth). In either case, it is desirable for the wear part to be securely held to the excavating equipment to prevent loss during use, and yet be capable of being removed and installed to facilitate replacement when worn. In order to minimize equipment downtime, it is desirable for the worn wear part to be capable of being easily and quickly replaced in the field. Wear parts are usually formed of three (or more) components in an effort to minimize the amount of material that must be replaced on account of wearing. As a result, the wear part generally includes a support structure that is fixed to the excavating equipment, a wear member that mounts to the support structure, and a lock to hold the wear member to the support structure.
As one example, an excavating tooth usually includes an adapter as the support structure, a tooth point or tip as the wear member, and a lock or retainer to hold the point to the adapter. The adapter is fixed to the front digging edge of an excavating bucket and includes a nose that projects forward to define a mount for the point. The adapter may be a single unitary member or may be composed of a plurality of components assembled together. The point includes a front digging end and a rearwardly opening socket that receives the adapter nose. The lock is inserted into the assembly to releasably hold the point to the adapter.
The lock for an excavating tooth is typically an elongate pin member which is fit into an opening defined cooperatively by both the adapter and the point. The opening may be defined along the side of the adapter nose, as in U.S. Pat. No. 5,469,648, or through the nose, as in U.S. Pat. No. 5,068,986. In either case, the lock is inserted and removed by the use of a large hammer. Such hammering of the lock is an arduous task and imposes a risk of harm to the operator.
The lock is usually tightly received in the passage in an effort to prevent ejection of the lock and the concomitant loss of the point during use. The tight fit may be effected by partially unaligned holes in the point and adapter that define the opening for the lock, the inclusion of a rubber insert in the opening, and/or close dimensioning between the lock and the opening. However, as can be appreciated, an increase in the tightness in which the lock is received in the opening further exacerbates the difficulty and risk attendant with hammering the locks into and out of the assemblies.
The lock additionally often lacks the ability to provide substantial tightening of the point onto the adapter. While a rubber insert will provide some tightening effect on the tooth at rest, the insert lacks the strength needed to provide any real tightening when under load during use. Most locks also fail to provide any ability to be re-tightened as the parts become worn. Moreover, many locks used in teeth are susceptible to being lost as the parts wear and the tightness decreases.
These difficulties are not limited strictly to the use of locks in excavating teeth, but also apply to the use of other wear parts used in excavating operations. In another example, the adapter is a wear member that is fit onto a lip of an excavating bucket, which defines the support structure. While the point experiences the most wear in a tooth, the adapter will also wear and in time need to be replaced. To accommodate replacement in the field, the adapters can be mechanically attached to the bucket. One common approach is to use a Whisler style adapter, such as disclosed in U.S. Pat. No. 3,121,289. In this case, the adapter is formed with bifurcated legs that straddle the bucket lip. The adapter legs and the bucket lip are formed with openings that are aligned for receiving the lock. The lock in this environment comprises a generally C-shaped spool and a wedge. The arms of the spool overlie the rear end of the adapter legs. The outer surfaces of the legs and the inner surfaces of the arms are each inclined rearward and away from the lip. The wedge is then ordinarily hammered into the opening to force the spool rearward. This rearward movement of the spool causes the arms to tightly pinch the adapter legs against the lip to prevent movement or release of the adapter during use. As with the mounting of the points, hammering of the wedges into the openings is a difficult and potentially hazardous activity.
In many assemblies, other factors can further increase the difficulty of removing and inserting the lock when replacement of the wear member is needed. For example, the closeness of adjacent components, such as in laterally inserted locks (see, e.g., U.S. Pat. No. 4,326,348), can create difficulties in hammering the lock into and out of the assembly. Fines can also become impacted in the openings receiving the locks making access to and removal of the locks difficult. Additionally, in Whisler style attachments, the bucket must generally be turned up on its front end to provide access for driving the wedges out of the assembly. This orientation of the bucket can make lock removal difficult and hazardous as the worker must access the opening from beneath the bucket and drive the wedge upward with a large hammer. The risk is particularly evident in connection with dragline buckets, which can be very large. Also, because wedges can eject during service, it is common practice in many installations to tack-weld the wedge to its accompanying spool, thus, making wedge removal even more difficult.
There has been some effort to produce non-hammered locks for use in excavating equipment. For instance, U.S. Pat. Nos. 5,784,813 and 5,868,518 disclose screw driven wedge-type locks for securing a point to an adapter and U.S. Pat. No. 4,433,496 discloses a screw-driven wedge for securing an adapter to a bucket. While these devices eliminate the need for hammering, they each require a number of parts, thus, increasing the complexity and cost of the locks. The ingress of fines can also make removal difficult as the fines increase friction and interfere with the threaded connections. Moreover, with the use of a standard bolt, the fines can build up and become “cemented” around the threads to make turning of the bolt and release of the parts extremely difficult.